Of course they didn't mention it, but at first look I noticed something I think is very interesting about the snippets they're showing, which caught my attention because of NOT including the search term used. It grabbed me so hard I'm tempted to post the specific search and site, but will be checking further for the next day or so to unravel it.

One site I am maintaining appears on top of Yahoo! result for a certain query using the description found at Yahoo! Directory. Which made me think if Yahoo! displays DMOZ directory description instead of its own directory entry (for sites that are listed there).

Another observation on snippets. On a couple of my pages, when checking the listings there's no snippet at all showing, just the page title and URL. Those particular pages have no meta description, seems it's time to add them where they're missing.